1. Field of the Invention
The invention relates to pulse oximeters and methods for expressing the urgency of the patient""s condition to the monitoring individuals.
2. Description of the Related Art
Pulse oximeters measure the oxygen saturation in pulsatile arterial blood by analyzing the variations in light transmission through a section of body tissue, and are well-known in the art. As disclosed by Wood in U.S. Pat. No. 2,706,927, the oxygen saturation can be calculated from two measurements of light absorption at two different wavelengths by a section of body tissue. The quantity of arterial blood in a section of body tissue varies in synchroneity with the heartbeat, so heartbeat-synchronized variations in the transmitted light intensity therefore correspond to variations of the pulsatile arterial blood. Because the absorption coefficient of the oxyhemoglobin component of blood can be determined, a comparison of the transmitted light intensities at different moments during the periodic heartbeat can be converted into a measure of the fraction of oxyhemoglobin in arterial blood, i.e., the arterial oxygen saturation. Various methods of calculating the oxygen saturation level are known in the prior art, such as, for example, the methods disclosed in Diab et al., U.S. Pat. No. 5,632,272, issued May 27, 1997.
The present inventors recognized several disadvantages inherent in the pulse oximeter monitor technology described in the prior art. First, in order to be able to interpret the information contained in the variations of the pitch of the audible sounds created by the prior art devices, a health care individual such as a nurse must be able to put the audible sounds in the correct context. To audibly detect a problem, the individual must have some experience in discerning the difference between a sound pitch which is within tolerances and a sound pitch which is indicative of a problem. Using sound pitch as the measure of oxygen saturation therefore requires cognitive thought by the individual who has been trained to recognize the sound pitches associated with low oxygen saturation conditions. Such high-level thought processes occur more slowly, and are more prone to mistakes in judgment, than are other, more instinctive, thought processes. Second, the monitors described in the prior art which use sound pitch as an indication of low oxygen saturation do not exploit the psychological response of humans to associate particular sounds with danger or trouble. Because there is nothing inherent in the pitch of a sound itself which is indicative of a problem, individuals must use high-level thought processes to translate the change of sound pitch into a measure of the patient""s condition. Third, various individuals have different abilities to detect differences or changes in sound pitch. Ear defects or injuries of the individual monitoring the patient""s condition can impact the individual""s ability to immediately detect a problem with the patient""s oxygen saturation.
It is an object of the present invention to provide a monitor for a pulse oximeter which emits an audible sound containing information regarding the patient""s condition that requires less training and subjective judgment by the individual monitoring the patient""s condition.
It is another object of the present invention to provide a monitor for a pulse oximeter which emits an audible sound containing information regarding the patient""s condition that can be more quickly interpreted by the individual monitoring the patient""s condition.
It is also another object of the present invention to provide a monitor for a pulse oximeter which emits an audible sound containing information regarding the patient""s condition that is less affected by hearing disabilities of the individual monitoring the patient""s condition.
One aspect of the present invention is a monitor for a pulse oximeter for use in measuring a patient""s pulse rate and oxygen saturation level. The monitor comprises a generator which generates an audio signal. The audio signal contains information regarding the patient""s pulse rate and oxygen saturation level. A transducer is coupled to the generator to receive the audio signal and to convert the audio signal into audible sounds containing information regarding the patient""s pulse rate and oxygen saturation level. Unlike the prior devices, the information is not contained in variations of the pitch of the audible sounds.
Another aspect of the present invention is a monitor for a pulse oximeter for use in measuring a patient""s pulse rate and oxygen saturation level. The monitor comprises a generator which generates an audio signal which varies in response to the patient""s pulse rate and oxygen saturation level. A transducer is coupled to the generator to receive the audio signal. The transducer converts the audio signal into audible sounds having a volume responsive to the patient""s pulse rate and oxygen saturation level.
Another aspect of the present invention is a monitor for a pulse oximeter for use in measuring a patient""s pulse rate and oxygen saturation level. The monitor comprises a generator which generates an audio signal which varies in response to the patient""s pulse rate and oxygen saturation level. A transducer is coupled to the generator to receive the audio signal. The transducer converts the audio signal into audible sounds with pitches of constant frequency. The audible sounds are responsive to the patient""s pulse rate and oxygen saturation level.